Comparative Analysis of Discharge Sensitivity by the Free Metal Particles in C4F7N/CO2 and SF6/N2 Gas Mixtures Under DC Electric Field

摘要

The electrical performance of DC GIL using SF₆ gas mixture or alternative gas as insulation medium will be deteriorated by free metal particles. The analysis of the factor affecting the insulation strength of SF₆/N₂ and C₄F₇N/CO₂ gas mixtures is mainly performed in this paper. The breakdown experiments with particle were conducted with the ball-bowl electrode under the DC electric field, which included different gas compositions such as C₄F₇N/CO₂ (4%/96%) gas mixture, SF₆/N₂ (volume ratio of SF₆ includes: 20%, 30%, 50%, and 70%, respectively) gas mixtures and pure SF₆ gas. The concept of Discharge Sensitivity by Particles(DSP) were proposed to evaluate the sensitivity of the insulation strength of different compositions gas to the electric field distortion caused by metal particles. The experiment results show that in the pressure range of 0.1 to 0.5 MPa, the dielectric strength of 4%C₄F₇N/96%CO₂ is equivalent to that of 30%SF₆/70%N₂ in the absence of particle, while due to the presence of particle, the DSP of 4%C₄F₇N/6%CO₂ gas mixture is higher than that of 20%SF₆/80%N₂ gas mixture and lower than that of 30%SF₆/70%N₂ gas mixture, accompanied by the appearance of discharge current of double peak. The high dielectric strength and low sensitivity to particle discharge of C₄F_展开▼